Snorkeling-related, swimming-related or coincidental deaths?

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In “Snorkelling-related deaths in Australia, 1994–2006” John M. Lippmann, et al. presented an analysis of 140 snorkeling-related deaths that occurred in Australia during the period of 1994-2006. The majority of the cases occurred due to cardiac-related causes (60) or drowning while at the surface (33). Only 19 deaths occurred after prolonged breath-hold diving and 10 were caused by trauma.

Cardiac cause was established based on medical examiners’ findings.

  • In 34 cases there was a history of cardiac disease.
  • In 19 cases cardiac pathology was established for the first time at autopsy.
  • The remaining five there was neither a history nor conclusive autopsy finding. Medical experts believed these five occurred as a result of cardiac arrhythmias.
  • Most deaths due to cardiac causes occurred in male snorkelers of a median age of 65, who were found silently floating in the water. Authors propose the term “fatal silent snorkeling syndrome” for these cases.

Overall, the incidence rate of snorkeling deaths is very small; with an average 10 cases per year and about 2 million snorkelers annually, it is approximately five deaths per 1 million snorkelers. In cases of cardiac death, there are about 2 deaths per 1 million snorkelers. While this small overall risk does not require any particular intervention, there are some people that may be at much higher risk. This includes individuals with a family history of sudden cardiac death and people with known heart disease. Among other causes of snorkeling death, there were four cases of epileptic seizures while snorkeling which may be either unrelated or provoked by water immersion (so called “water immersion epilepsy”).

There were only 19 breath-hold diving deaths including prolonged or deep diving in apnea; however, the number of people practicing breath-hold diving was not known and the relative risk could not be established. One may reasonably assume that true breath-hold diving involves greater risk than surface snorkeling (when controlled for age).

Snorkeling is widespread among recreational swimmers and does not necessarily involve submersion. Hazards for snorkelers are same as for swimmers, but statistics for drowning deaths were not compared here. According to this paper, in 2006 in Australia, out of 16 dive-related deaths, 10 were snorkeling related. Another source reports that diving-related deaths make up approximately 7% of drowning in open waters. Incidence rate for snorkeling deaths due to cardiac causes may not be different than incidence rate of drowning due to cardiac causes. The point is that “snorkeling deaths” and “swimming deaths,” with exclusion of true breath-hold diving deaths, may be the result of the same causes. While specific provocative factors may be present in immersion, beyond channelopathies and “immersion epilepsy,” they may not amount to a greater risk than the risk people are exposed to in their daily lives.

The paper brings out many other interesting details and is worth a read.

Post written by: Petar Denoble, MD, D.Sc.

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